Detecting volatile compounds in food by open-path Fourier-transform infrared spectroscopy.

We previously found that the brand of a food and spoilage of the food can be identified from the infrared spectra of the volatile compounds released. However, this required pumping the volatile compounds into a gas cell, meaning measurements over large areas could not be made. Gas components can be quantified from a distance of a few metres or kilometres by open-path Fourier-transform infrared spectroscopy (FTIR), and the spatial distributions of gas clouds can even be determined using open-path FTIR and an imaging detection method. In the study described here, we used open-path FTIR to remotely detect volatile compounds in food. Active and passive methods were used to obtain infrared spectra of volatile compounds released from spirits, vinegars, and grapes from a distance of 5 m. The absorption characteristics of ethanol, esters, and unknown volatile compounds were clearly found in the spectra. The brands of the spirits and degree to which the grapes had spoiled were identified by compensating for ethanol in the atmosphere and chemometrics. The results indicate that open-path FTIR can be used to remotely detect volatile compounds released by food and may be able to be used to identify spoiling food in large food warehouses.